An early sign of autism—declining eye contact—may be detected in infants as young as just a few months old, according to a recent study.

Researchers studied 110 infants, about half who were at high risk of developing autism spectrum disorder (ASD) and half who were at low risk. The investigators used eye-tracking equipment to measure the infants’ visual scanning. Infants who eventually were diagnosed with ASD had declining eye contact beginning at the age of 2 months. By age 2 years, their ability to make eye contact was about half that of children who didn’t develop ASD.